FUNCTIONAL-ANALYSIS OF THE PROMOTER REGION OF A MAIZE (ZEA-MAYS L.) H3 HISTONE GENE IN TRANSGENIC ARABIDOPSIS-THALIANA

A 1023 bp treatment and truncated derivatives of the maize (Zea mays L .) histone H3C4 gene promoter were fused to the beta-glucuronidase (GU S) gene and introduced via Agrobacterium tumefaciens into the genome o f Arabidopsis thaliana. GUS activity was found in various meristems of transgenic plants as for other plant histone promoters, but unexplain ed activity also occurred at branching points of both stems and roots. Deletion of the upstream 558 bp of the promoter reduced its activity to an almost basal expression. Internal deletion of a downstream fragm ent containing plant histone-specific sequence motifs reduced the prom oter activity in all tissues and abolished the expression in meristems . Thus, both the proximal and distal regions of the promoter appear ne cessary to achieve the final expression pattern in dicotyledonous plan t tissues. In mesophyll protoplasts isolated from the transformed Ambi dopsis plants, the full-length promoter showed both S phase-dependent and -independent activity, like other plant histone gene promoters. Ne ither of the 5'-truncated nor the internal-deleted promoters were able to direct S phase-dependent activity, thus revealing necessary cooper ation between the proximal and distal parts of the promoter to achieve cell cycle-regulated expression. The involvement of the different reg ions of the promoter in the different types of expression is discussed .